Porcine Proliferative Enteropathy (PPE, ileitis) is a disease of very great significance worldwide to the economics of pig production (Chouet et al. 2003, Wendt et al. 2006). The pathogen that causes the disease, Lawsonia intracellularis (L.i.), is spread through the faeces of the pigs and causes damage to the intestinal mucosa in the large and small bowel that is critical to the digestive function (Kroll et al. 2005).
For many years, different antibiotics have been licensed for the treatment of ileitis (=Lawsonia intracellularis infection). The active substances belong to the bacteriostatic antibiotics. They do not kill the pathogens directly but inhibit the multiplication of Lawsonia intracellularis (Armbuster et al. 2004, Busch et al. 2000, Collins et al. 2000a, Dritz et al. 2002, Kesl et al. 2004, Paradis 2004, Thaker and Bilkei 2006, Tzika et al. 2004, Veenhuizen et al. 1998a, Walter et al. 2000, Winkelman et al. 2000). For some years, a vaccine (Enterisol® Ileitis, made by Boehringer Ingelheim Vetmedica GmbH) has been available against the disease forms induced by Lawsonia intracellularis. The objective of the vaccination measures is to build up a reliable immunity before the first contact with the field pathogen. In order that the animals have developed a reliable immunity before the first field infection, the animals, particularly piglets, have to be vaccinated as early as possible, preferably in the first three weeks of life.
In Germany, a significant increase in clinical cases of ileitis has been observed in the last 12 months. This is due not least to the ban on antibiotic performance promoters that took effect on 1 Jan. 2006 (EC Regulation 1831, 2003). In addition, the number of farms that had infections occurring shortly after weaning (=removal from the mother sow) increased considerably. In these farms the question is how it is possible to meet the requirement of effectively vaccinating the piglets three weeks before the field infection.
In the prior art the combined administration of Lawsonia intracellularis vaccine and anti-Lawsonia antibiotic is described. For example, Armbruster et al. in 2006 describe a method in which 5-week-old piglets were vaccinated with Lawsonia intracellularis vaccine and 25 days after vaccination were treated with tylosin, an anti-Lawsonia antibiotic. However, such a treatment does not protect the animals from early and, in particular, early fulminant infections, such as are observed more and more frequently (Hardge et al. 2006, Steinheuer et al. 2007). On the one hand, the vaccination of the animals at 5 weeks old is carried out at a very late stage. On the other hand, the administration of tylosin from day 25 after vaccination is insufficient to prevent or alleviate corresponding early infections that occur during the period when the animals have not yet built up any reliable immunity. Besides Armbruster et al. 2004, Bornhorn 2007 also describes early attempts at a so-called embedded vaccination. Like the treatment plan used by Armbruster et al. 2004, the treatment plan described by Bornhorn is unable to prevent or alleviate early infections. The process described by Bornhorn is used to treat existing Lawsonia intracellularis infections.
The aim of the present invention was to provide a method of preventing or at least reducing early Lawsonia intracellularis infections.
A further aim of the present invention was to vaccinate animals successfully against Lawsonia intracellularis in spite of the early infection pressure caused by production methods.
A further aim of the present invention was to improve the general weight gain of animals, particularly animals for fattening, in spite of early infection with Lawsonia intracellularis caused by production methods.
These aims are achieved by the methods/uses described hereinafter.